A submersible pump is a centrifugal pump having a submersible motor that rotates a shaft to drive a pump. The submersible pump is for producing high volumes of oil and water. A typical submersible pump motor may be from 6-60 feet in length and be rated at several hundred horsepower. Each motor has a stator secured within a tubular housing. A rotor secured to the shaft rotates within a stator.
Because of the long length of the motor, the rotor is made up of a number of rotor sections. Each rotor section comprises a large number of flat disks called laminations that are secured by copper rods. The rotor sections are spaced apart from each other. A bearing assembly is located between each section for maintaining the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation therewith, but are axially movable with respect to the shaft.
Traditionally, the bearing assemblies used in motors, seal sections and pumps of electrical submersible pumps (ESPs) are plain sleeve bearings, which provide radial support. These plain sleeve bearings are not heavily loaded since a large number of bearings are typically used and the ESP units are run in a near vertical orientation. The absence of a substantial load results in an unstable or marginally stable bearing operation that can result in metal-to-metal contact in the bearings, which accelerates bearing failure. Presently, motors using plain sleeve bearings typically have a 50% success rate for passing a vibration test in a test well. Therefore, a need exists for a bearing type that increases the dynamic stability of the bearings.